The change of oxygen potential, ΔḠo2, for the solid solutions of general formula Ay2-Bz3+U1-y-zO 2+x was studied by the method of configurational entropy calculation for cations and cation complexes. A part of Mg atoms (fraction m) were assumed to occupy the interstitial 4b sites of the solid solution, and the number of ways of arranging the free ions and intra-cation complexes was calculated followed by differentiation of the logarithm of this number with respect to oxygen non-stoichiometry to obtain partial molar entropy of oxygen. As the complexes, (A2+U5+), (A2+2U5+) and (B3+U5+) were assumed to be formed. For the first two complexes, an average composition (A2+αU5+) was defined, and for (B3+U5+) a fraction, β, of B3+ was considered to form the complex. The O/M ratio (M = A + B + U) which gave the steepest change of ΔḠo2 was calculated. Below this O/M ratio to 2 - y - (1 - β)z/2, the solid solution possibly satisfied the relation m -X/(2y), where X = -x. In the region where this relation held, the solid solution was supposed to be oxygen stoichiometric.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering